Polymer compositions for temporary bonding

ABSTRACT

Embodiments in accordance with the present invention are directed to polymer compositions that are useful for forming temporary bonding layers that serve to releasably join a first substrate to a second substrate as well as methods of both forming such a temporary bond and methods of debonding such substrates. Some such polymer compositions encompass a casting solvent, a photoacid generator and optionally a sensitizer and/or an adhesion promoter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Non-provisional application and claims the benefitof priority to prior Provisional application Ser. No. 61/427,859 filedDec. 29, 2010, the entire contents of which are hereby incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates generally to polymers that are useful forforming temporary or releasable bonds.

BACKGROUND

U.S. Pat. No. 7,713,835 (hereinafter '835), entitled “Thermallydecomposable spin-on bonding compositions for temporary wafer bonding”issued May 11, 2010 to Brewer Science Inc., described problemsassociated with prior art methods and materials used to form temporarybonds between semiconductor wafers and carrier substrates. The '835patent asserts that such prior art problems are overcome by providing awafer bonding method where a stack comprising first and secondsubstrates bonded together via a bonding composition layer is exposed toa temperature of at least about 285° C. and preferably from 350° C. to400° C. so as to thermally decompose the bonding composition layer andcause the substrates to separate.

While such a decomposable material as disclosed by the '835 patent islikely to be useful for applications where a debonding temperature at orabove 285° C. can be tolerated by wafers and substrates, manyapplications where a temporary or releasable bond would be useful cannotwithstand such elevated temperatures. Therefore it would be advantageousto provide bonding compositions for temporary wafer bonding that can bedebonded at temperatures at or below a temperature employed for formingsuch a bond, where such temperature is at or below 200° C.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 depicts a flow chart of a processing method embodiment inaccordance with the present invention.

DETAILED DESCRIPTION

Described herein are materials that can form releasable or temporarybonds, where at a first temperature the materials remain in a fixed modeduring one or more desired process steps and subsequently are madereleasable at a second temperature equal to or lower than the firsttemperature. Embodiments in accordance with the present invention aregenerally directed to providing polymer compositions that are capable offorming films for use as a temporary (or releasable) bonding layeruseful in the manufacture of microelectronic and optoelectronic devices.

Embodiments in accordance with the present invention are directed toproviding polymer compositions, such as poly(lactide) compositions, andnon-poly(lactide) polymer compositions that are capable of forming filmsfor use as a temporary (or releasable) bonding layer useful in themanufacture of microelectronic and optoelectronic devices. In someembodiments, such polymer compositions are capable of forming a bondinglayer having a thickness in excess of 30 microns with a single coatingoperation, where such a bonding layer maintains a fixed bond, onceformed, that exhibits thermal stability to temperatures of at least 200°C. while allowing for debonding at temperatures at or below 200° C.after an appropriate exposure to actinic radiation.

Other embodiments in accordance with the present invention are directedto providing multi-layered films, such as a poly(lactide) layer and atleast one other non-poly(lactide) polymer layer or two non-poly(lactide)polymer layers that are capable of forming multi-layered films for useas a temporary (or releasable) bonding layer useful in the manufactureof microelectronic and optoelectronic devices. In such embodiments, suchmulti-layered films encompass a bonding layer that exhibits thermalstability at a first temperature, such as at least 200° C., whileallowing for debonding at a second temperatures, typically below thefirst temperature such as at or below 200° C. Such debonding being theresult of one layer being depolymerized under specific conditions suchas exposure to actinic radiation and/or heating to the aforementionedsecond temperature.

Unless otherwise indicated, all numbers, values and/or expressionsreferring to quantities of ingredients, reaction conditions, etc., usedherein are to be understood as modified in all instances by the term“about” as absent the aforementioned indication, such numbers areapproximations reflective of, among other things, the variousuncertainties of measurement encountered in obtaining such values.Further, where a numerical range is disclosed herein such range iscontinuous, and includes every value between the minimum and maximumvalues of such range. Still further, where a range refers to integers,every integer from the minimum to the maximum values of such range isincluded. In addition, where multiple ranges are provided to describe afeature or characteristic, such ranges can be combined.

As used herein, the terms “polymer composition”, “poly(lactide)composition” and “non-poly(lactide) composition” are meant to includeone or more synthesized polymers, as well as residues from initiators,catalysts, and other elements attendant to the synthesis of suchpolymer(s) or the forming of such polymer compositions, where suchresidues are understood as not being covalently incorporated thereto.Such residues and other elements considered as part of the polymercomposition are typically mixed or co-mingled with the polymer(s) suchthat they tend to remain therewith when it is transferred betweenvessels or between solvent or dispersion media. A polymer compositioncan also include materials added after synthesis of the polymer(s) toprovide to or modify specific properties of such a composition.

As used herein, the term “PLA” refers to substituted and unsubstitutedpoly(lactides). As used herein, the term “NPL” refers to substituted andunsubstituted polymers where the polymer is not a poly(lactide) norcontains lactide repeat units.

Where such PLAs or NPLs are referred to as being substituted, suchreference will be understood to mean that at least one of the lactiderepeating units or other polymer repeating units encompasses ahydrocarbyl substituent having from 1 to 12 carbon atoms. Where, as usedherein, the term “hydrocarbyl” refers to a radical or a group thatgenerally contains only carbon and hydrogen atoms. Non-limiting examplesof such hydrocarbyl groups being alkyl or cycloalkyl.

It will also be understood that some embodiments in accordance with thepresent invention may include “heterohydrocarbyl” groups where such termrefers to any of the previously described hydrocarbyls, where at leastone carbon atom of the carbon chain is replaced with N, O, S, Si or P.It will additionally be understood that any of the hydrocarbyl orheterohydrocarbyl moieties described above can be further substituted,if desired.

The polymer composition embodiments in accordance with the presentinvention that are capable of forming temporary bonding layers exhibitcontrollable bonding or adhesive differences that permit relativelystrong bonding between two structures under a first set of conditionsand relatively weak bonding between the two structures under a secondset of conditions. Examples of polymers suitable for use in such polymercompositions include, but are not limited to, homopolymers having onlyone lactide-type repeating units, polymers having two or morelactide-type repeating units, and polymers having lactide repeatingunits and repeating units derived from other types of monomers.

PLAs are commercially available under the trade designation Ingeo™ fromNatureWorks LLC of Minnetonka, Minn.; and under the trade designationPURASORB® from Purac of Gorinchem, The Netherlands. Specific examples ofPLAs from Purac include PLDL 7017 (70% L-lactide and 30% DL-lactide withan inherent viscosity midpoint of 1.7 dl/g), PLDL7025 (70% L-lactide and30% DL-lactide with an inherent viscosity midpoint of 2.5 dl/g),PLDL7038 (70% L-lactide and 30% DL-lactide with an inherent viscositymidpoint of 3.8 dl/g), and PDL20 (100% DL-lactide with an inherentviscosity midpoint of 2.0 dl/g).

Alternatively, PLAs can be made using known techniques. For example, bya tin-catalyzed ring-opening polymerization. An example of such a tincatalyst is Sn(II) octanoate which has been found useful for bulkpolymerization of lactide monomers. Such tin catalysts have highcatalytic activity, a low rate of racemization of the polymer andprovide conversions greater than 90% with high Mw. Typical conditionsfor such ring-opening polymerizations are temperatures from 180 to 210°C., from 100-1000 ppm of the tin catalyst and a reaction time of from 2to 5 hours. Monomers useful for forming the polymer embodiments inaccordance with the present invention include substituted andunsubstituted lactides. When such monomers are substituted, ahydrocarbyl group having 1 to 12 carbons is typically the substituent.It should be noted that lactides monomers have stereochemicaldifferences that can be exploited to control and or modify the thermal,barrier, and solubility properties of subsequently formed polymers. Forexample, different monomers (or different amounts of selected monomers)can be employed to tailor desired properties of a given, subsequentlyformed polymer. Thus where polymers rich in L-lactide are formed, suchpolymers tend to be crystalline while polymers formed with more than 15%D-lactide tend to be more amorphous. The chemical structures of varioustypes of lactide monomers are shown below.

As used herein, and unless otherwise stated, thermogravimetric analysis(TGA), here at a heating rate of 10° C./minute, is reported as a measureof the thermal stability of the variety of polymers encompassed by theembodiments in accordance with the present invention. Specifically theTd₅, Td₅₀ and Td₉₅ values, indicative that 5, 50 and 95 weight percent(wt %) of a polymer has been decomposed (lost by vaporization) have beendetermined as seen in Table 1, below:

TABLE 1 Polymer Composition Td (5%) Td (50%) Td (95%) PLDL7038 Polymerof L-lactide and 297° C. 347° C. 367° C. DL-lactide 70/30 PLDL 7025Polymer of L-lactide and 329° C. 363° C. 380° C. DL-lactide 70/30 PDL20Polymer of DL-lactide 327° C. 362° C. 380° C.

Useful types of monomers for embodiments in accordance with the presentinvention are described generally above and further described by thetypes of monomer structures provided herein. For some embodiments inaccordance with the present invention, the polymer compositionencompasses a blend of two or more PLA polymers where such polymers canbe homopolymers or not. That is to say that such polymers can have onetype of repeating unit or more than one type of repeating unit,respectively. In other embodiments, the polymer composition encompassesonly one PLA polymer where such polymer can be a homopolymer or not. Inone exemplary embodiment, the polymer composition encompasses about 70mole percent L-lactide and about 30 mole percent DL-lactide by weight ofthe composition (PLDL7025).

It should also be noted that polymer embodiments that encompassrepeating units derived from monomers other than lactide-type monomersare contemplated herein. Further, polymer composition embodiments thatencompass both lactide-type polymers and polymers having both repeatingunits derived from lactide-type monomers and non-lactide-type monomersare also contemplated herein. For example, a polymer composition inaccordance with the present invention can encompass a first polymerhaving one or more repeating units derived only from lactide-typemonomers as well as a second polymer encompassing one or more repeatingunits derived from lactide-type repeating units and one or morerepeating units derived from non-lactide-type repeating units. Alsoencompassed are embodiments where multi-layered films are provided,where at least one polymer layer contains a PLA polymer and at least onepolymer layer contains a NPL polymer.

It should further be noted that polymer embodiments of single layeredfilms encompass NPL polymers. Examples of NPL polymers for singlelayered temporary bonding films include polycarbonates, polyesters,polyamides, polyethers, polymethacrylates, polynorbornenes,alkylcelluloses and combinations of two or more thereof. Alsoencompassed are embodiments where multi-layered films are provided,where at least one polymer layer contains a NPL polymer and at least onepolymer layer contains a different NPL polymer.

Examples of NPL polymers include polycarbonates, polyesters, polyamides,polyethers, polymethacrylates, polynorbornenes, alkylcelluloses andcombinations of two or more thereof. That is, NPL polymers can containrepeat units from one or more of polycarbonates, polyesters, polyamides,polyethers, polymethacrylates, and polynorbornenes.

Examples of polycarbonates include, but are not limited to, 1,2-butylenecarbonate, 1,3-butylene carbonate, 1,4-butylene carbonate,cis-2,3-butylene carbonate, trans-2,3-butylene carbonate,α,β-isobutylene carbonate, α,γ-isobutylene carbonate,cis-1,2-cyclobutylene carbonate, trans-1,2-cyclobutylene carbonate,cis-1,3-cyclobutylene carbonate, trans-1,3-cyclobutylene carbonate,hexene carbonate, cyclopropene carbonate, cyclohexene carbonate,(methylcyclohexene carbonate), (vinylcyclohexene carbonate),dihydronaphthalene carbonate, hexahydrostyrene carbonate, cyclohexanepropylene carbonate, styrene carbonate, (3-phenylpropylene carbonate)(3-trimethylsilyloxypropylene carbonate) (3-methacryloyloxypropylenecarbonate), perfluoropropylene carbonate, norbornene carbonate,polypropylene carbonate/polycyclohexene carbonate copolymer,poly[(oxycarbonyloxy-1,1,4,4-tetramethylbutane)-alt-(oxycarbonyloxy-5-norbornene-2-endo-3-endo-dimetan)],poly[(oxycarbonyloxy-1,4-dimethylbutane)-alt-(oxycarbonyloxy-5-norbornene-2-endo-3-endo-dimetan)],poly[(oxycarbonyloxy-1,1,4,4-tetramethylbutane)-alt-(oxycarbonyloxy-p-xylene)],poly[(oxycarbonyloxy-1,4-dimethylbutane)-alt-(oxycarbonyloxy-p-xylene)], polycyclohexenecarbonate/polynorbornene carbonate copolymer, and combinations of two ormore thereof.

Examples of polyesters include, but are not limited to, amorphouscopolyesters such as RV270 and GK880 both obtained from Toyobo America,Inc., and polyesters formed from monomers such as1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and2,2-dimethyl-1,3-propanediol (Sigma Aldrich).

Examples of polymethacrylates include, but are not limited to, methylmethacrylate-methacrylic acid (80/20) copolymer (Monomer-Polymer & DajacLabs, Trevose, Pa., product number 9425) and methyl methacrylate-butylacrylate triblock copolymers such as LA 2250, LA 4285 and LA 2140eavailable from Kuraray America, Inc,

Examples of alkylcelluloses include, but are not limited to,methylcellulose, ethylcellulose and hydroxy propylcellulose allavailable from Sigma Aldrich.

For some embodiments in accordance with the present invention, theweight average molecular weights (Mw) of such NPLs, is in the range of1,000 to 1,000,000. In other embodiments, the Mw is from 5,000 to700,000 and in still others from 10,000 to 500,000. Weight averagemolecular weights that are not below 1,000 typically provide one or moreadvantageous effects including: improved wettability of the fixedpolymer layer to the semiconductor wafer or support substrate, andimproved film-forming properties. Weight average molecular weights thatare not higher than 1,000,000 typically provide one or more advantageouseffects including: improved compatibility of the polymer to variouscomponents in the fixed polymer layer and the solubility thereof tovarious solvents, and improved thermal depolymerizability of the fixedpolymer layer in a debonding act (such as separating a wafer from asubstrate).

Methods of polymerizing polycarbonate polymers include art-recognizedmethods, such as, a phosgene method (solvent method) and atransesterification method (melting method) among others.

Examples of norbornene-type polymers that can be used herein includethose having structural units represented by the following generalformula (1):

With reference to formula (1), m is an integer of 0 to 4; and R¹, R², R³and R⁴ each represent a hydrogen atom, or a hydrocarbyl pendent groupcontaining from 1 to 20 carbon atoms, such as a linear or branched alkylgroup, an aromatic group, or an alicyclic group having 1 to 20 carbonatoms; a halohydrocarbyl containing from 1 to 20 carbon atoms; aperhalocarbyl containing from 1 to 20 carbon atoms; and siliconcontaining hydrocarbyl group such as a substituent represented by thefollowing general formula (2).

With reference to formula (2), each R⁵ independently represents ahydrogen atom, a methyl group, or an ethyl group; R⁶, R⁷, and R⁸ eachindependently represent a linear or branched alkyl group having 1 to 20carbon atoms, a linear or branched alkoxy group having 1 to 20 carbonatoms, a linear or branched alkylcarbonyloxy group having 1 to 20 carbonatoms and a substituted or unsubstituted aryloxy group having 6 to 20carbon atoms; and n is an integer of 0 to 5.

As used herein, “hydrocarbyl” refers to a radical or group that containsa carbon backbone where each carbon is appropriately substituted withone or more hydrogen atoms. The term “halohydrocarbyl” refers to ahydrocarbyl group where one or more of the hydrogen atoms, but not all,have been replaced by a halogen (F, Cl, Br, I). The term perhalocarbylrefers to a hydrocarbyl group where each hydrogen has been replaced by ahalogen. Non-limiting examples of hydrocarbyls, include, but are notlimited to a linear or branched C₁-C₂₀ alkyl, a linear or branchedC₂-C₂₀ alkenyl, a linear or branched C₂-C₂₀ alkynyl, a linear orbranched C₅-C₂₅ cycloalkyl, an C₆-C₂₀ aryl, or an C₇-C₂₀ aralkyl.Representative alkyl groups include but are not limited to methyl,ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl and dodecyl.Representative alkenyl groups include but are not limited to vinyl.Representative alkynyl groups include but are not limited to ethynyl,1-propynyl, 2-propynyl, 1 butynyl, and 2-butynyl. Representativecycloalkyl groups include but are not limited to cyclopentyl,cyclohexyl, and cyclooctyl substituents. Representative aryl groupsinclude but are not limited to phenyl, biphenyl, naphthyl, andanthracenyl. Representative aralkyl groups include but are not limitedto benzyl, and phenethyl.

The term halohydrocarbyl as used throughout the present specification isinclusive of the hydrocarbyl moieties mentioned above but where there isa degree of halogenation that can range from at least one hydrogen atombeing replaced by a halogen atom (e.g., a fluoromethyl group) to whereall hydrogen atoms on the hydrocarbyl group have been replaced by ahalogen atom (e.g., trifluoromethyl or perfluoromethyl), also referredto as perhalogenation.

In other embodiments in accordance with the invention, one or more ofR¹, R², R³, and R⁴ is a linear or branched C₁ to C₂₀ hydrocarbyl,halohydrocarbyl or perhalocarbyl pendent group, where such hydrocarbyl,halohydrocarbyl or perhalocarbyl group encompasses one or moreheteroatoms selected from O, N, S, P and Si, and the others of R¹, R²,R³, and R⁴ are H. Exemplary groups encompassing heteroatoms include,among others, a triethoxysilyl group a methanol acetate group, at-butylcarboxylate group and a hindered phenol group such as representedby structural formula A:

For embodiments in accordance with the present invention, when a linearor branched alkyl pendent group having 1 to 20 carbon atoms is selectedfrom butyl, hexyl and decyl, the repeating units encompassing such alkylpendent groups provide desirable properties to the polymer such as oneor more of excellent compatibility with various components of atemporary bonding agent, solubility with various kinds of solvents, andmechanical physical properties when bonding together a semiconductorwafer and a support substrate. Similarly, for embodiments, havingaromatic pendent groups such as phenethyl and naphthyl, or alicyclicpendent groups such as cyclohexyl and norbornyl, desirable physicalproperties are also obtained.

For embodiments in accordance with the present invention that encompasspendent groups represented by formula (2), when the R⁵ group ishydrogen, desirable physical properties are also obtained. For someembodiments encompassing pendent groups represented by for formula (2),when R⁶, R⁷, and R⁸ are each independently selected from methoxy,ethoxy, and propoxy, desirable physical properties are also obtained,for example excellent adhesion to a support substrate. For someembodiments encompassing pendent groups represented by for formula (2),when n is 0 and the silyl group is directly bonded to a polycyclic ringvia a silicon-carbon bond, the resultant polymer layer also can providedesirable properties.

Norbornene-type polymers useful for method embodiments in accordancewith the present invention can include a single type of repeat unit or aplurality of different types of repeat units, each type of repeat unitbeing represented by the above formula (1).

Exemplary norbornene-type polymers having a single type of repeat unit,also referred to as homopolymers, include but are not limited topolynorbornene, poly(methyl norbornene), polyethyl norbornene),poly(butyl norbornene), poly(hexyl norbornene), poly(decyl norbornene),poly(phenethyl norbornene), poly(triethoxysilyl norbornene),poly(trimethylsilyl norbornene), poly(trimethoxysilyl norbornene),poly(methyldimethoxysilyl norbornene) and poly(dimethyl methoxynorbornene). Exemplary norbornene-type polymers having two or more typesof repeat units include, but are not limited to, anorborneneftriethoxysilyl norbornene polymer a butylnorbornene/triethoxysilyl norbornene polymer, and a decylnorborneneftriethoxysilyl norbornene polymer.

The weight average molecular weight (M_(w)) of norbornene-type polymersin accordance with embodiments of the present invention can be from5,000 to 1,000,000 Dalton, from 25,000 to 750,000 Dalton or from 40,000to 500,000 Dalton. For the above ranges of molecular weight, it will beunderstood that such values are obtained using polystyrene standards forgel permeation chromatography (GPC) with tetrahydrofuran (THF) as asolvent.

Norbornene polymers having structural units represented by the abovegeneral formula (1) can be prepared by any known methods including, forexample, vinyl addition polymerization methods.

Further to the polymer composition embodiments in accordance with thepresent invention, such compositions encompass a polymer embodiment, acasting solvent and optionally a photosensitizer, a photoacid generator(PAG) and/or an adhesion promoter. In embodiments where the bondinglayer contains multi-layered polymer films, at least one polymer layergenerally contains a PAG. In some embodiments, the polymer compositions,whether PLA or NPL polymer compositions, contain from 5 to 50 wt %polymer and from 0 to 5 wt % PAG. In another embodiments, the polymercompositions, whether PLA or NPL polymer compositions, contain from 10to 40 wt % polymer, from 0.05 to 2 wt % PAG.

PAGs useful for the polymer composition embodiments of the presentinvention can be selected from triphenylsulfonium salts such astriphenylsulfonium tris[(trifluoromethyl)sulfonyl]methanide;triphenylsulfonium 4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine1,1,3,3-tetraoxide (TPS N3); and triphenylsulfoniumtris[(trifluoromethyl)sulfonyl]methanide (TPS C1); thio aromatic acylsubstituted triphenylsulfonium salts such astris[4-[(4-acetylphenyl)thio]phenyl]sulfoniumtris[(trifluoromethyl)sulfonyl]methanide (GSID26-1); and naphthalenesubstituted sulfonium salts such as(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumtetrakis(pentafluorophenyl)borate (TAG 382);(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumtris[(trifluoromethyl)sulfonyl]methanide; and(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumtrifluorotris(1,1,2,2,2-pentafluoroethyl)phosphate.

Other ionic PAGs include triphenylsulfoniumtetrakis(pentafluorophenyl)borate; triphenylsulfoniumhexafluorophosphate; triphenylsulfonium hexafluoroantimonate;triphenylsulfonium nonafluorobutane sulfonate; triphenylsulfoniumtrifluoromethanesulfonate; triphenylsulfonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide (TPSN1); tris(4-t-butylphenyl)sulfonium tetrakis(pentafluorophenyl)borate;tris(4-t-butylphenyl)sulfonium hexafluorophosphate;tris(4-t-butylphenyl)sulfonium hexafluoroantimonate;tris(4-t-butylphenyl)sulfonium nonafluorobutane sulfonate;tris(4-t-butylphenyl)sulfonium trifluoromethanesulfonate;tris(4-t-butylphenyl)sulfonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide;tris(4-t-butylphenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methanide;triphenylsulfonium 4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine1,1,3,3-tetraoxide; tris(4-t-butylphenyl)sulfoniumtris[(trifluoromethyl)sulfonyl]methanide;tris[4-[(4-acetylphenyl)thio]phenyl]sulfoniumtetrakis(pentafluorophenyl)borate;tris[4-[(4-acetylphenyl)thio]phenyl]sulfonium hexafluorophosphate;tris[4-[(4-acetylphenyl)thio]phenyl]sulfonium hexafluoroantimonate;tris[4-[(4-acetylphenyl)thio]phenyl]sulfonium nonafluorobutanesulfonate; tris[4-[(4-acetylphenyl)thio]phenyl]sulfoniumtrifluoromethanesulfonate; tris[4-[(4-acetylphenyl)thio]phenyl]sulfonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide;tris[4-[(4-acetylphenyl)thio]phenyl]sulfonium4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine 1,1,3,3-tetraoxide;tris[4-[(4-acetylphenyl)thio]phenyl]sulfoniumtris[(trifluoromethyl)sulfonyl]methanide;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumhexafluorophosphate;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumhexafluoroantimonate;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumnonafluorobutane sulfonate;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumtrifluoromethanesulfonate;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfonium4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine 1,1,3,3-tetraoxide;(2-(4-methoxynaphthalen-1-yl)-2-oxoethyl)dimethylsulfoniumtris[(trifluoromethyl)sulfonyl]methanide; 5-phenyl-thianthreniumtetrakis(pentafluorophenyl)borate; 5-phenyl-thianthreniumhexafluorophosphate; 5-phenyl-thianthrenium hexafluoroantimonate;5-phenyl-thianthrenium nonafluorobutane sulfonate;5-phenyl-thianthrenium trifluoromethanesulfonate; 5-phenyl-thianthrenium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide;5-phenyl-thianthrenium tris[(trifluoromethyl)sulfonyl]methanide;5-phenyl-thianthrenium 4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine1,1,3,3-tetraoxide; 5-phenyl-thianthreniumtris[(trifluoromethyl)sulfonyl]methanide;1,4-phenylenebis[diphenylsulfonium]tetrakis(pentafluorophenyl)borate;1,4-phenylenebis[diphenylsulfonium]hexafluorophosphate;1,4-phenylenebis[diphenylsulfonium]hexafluoroantimonate;1,4-phenylenebis[diphenylsulfonium]nonafluorobutane sulfonate;1,4-phenylenebis[diphenylsulfonium]trifluoromethanesulfonate;1,4-phenylenebis[diphenylsulfonium]1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide;1,4-phenylenebis[diphenylsulfonium]tris[(trifluoromethyl)sulfonyl]methanide;1,4-phenylenebis[diphenylsulfonium]-4,4,5,5,6,6-hexafluorodihydro-4H-1,3,2-dithiazine1,1,3,3-tetraoxide;1,4-phenylenebis[diphenylsulfonium]tris[(trifluoromethyl)sulfonyl]methanide.

Additionally, non-ionic PAGs such as CGI-1906:2-[2,2,3,3,4,4,4-heptafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene;and CGI-1907:2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorenecan also be useful.

Examples of photosensitizers include anthracenes, phenanthrenes,chrysenes, benzpyrenes, fluoranthenes, rubrenes, pyrenes, xanthones,indanthrenes, thioxanthen-9-ones, or mixtures thereof. More specificallyanthracene-9-carboxylic acid can be useful as a sensitizer and9,10-dibutoxyanthracene, 9,10-diethoxyanthracene,1-chloro-4-propoxythioxanthone and chlorothioxanthone can also be usefulphotosensitizers. It should be noted that where a methacrylate polymeris selected for forming a polymer layer, such polymers do not generallyrequire the addition of a PAG to cause depolymerization. Rathergenerally only a photosensitizer additive is needed to provideactivation of the depolymerization reaction at a desired wavelength ofactinic radiation.

Exemplary casting solvents include, among others, N-methyl-pyrrolidone(NMP), propylene glycol monomethyl ether acetate (PGMEA),gamma-butyrolactone (GBL), and di-methyl-acetamide (DMAc). Other castingsolvents include, mixtures of PGME with PGMEA and mixtures of PGME withethyl lactate. Still other casting solvents include, glycerol,dibutylether, ethyl lactate dibutylglycerol, dimethyl sulfoxide (DMSO),dimethylformamide (DMF), high boiling aromatic-based solvents, petroleumether, the carbitol family, dipropyleneglycol and the glycol etherfamily, isobutyl alcohol (IBA), methyl isobutyl carbinol (MIBC),propylene glycol monomethyl ether (PGME), alcohols such as butanol, andmixtures thereof.

Examples of adhesion promoters includebis[(3-triethoxysilyl)propyl]disulfide (trade designation SIB 1824.6),allyl trimethoxysilane (trade designation SIA 0540),1,6-bis(trimethoxysilyl)hexane (trade designation SIB 1832). SIB 1824.6,SIA 0540, and SIB 1832 are commercially available from Gelest, Inc.

Some embodiments in accordance with the present invention are directedto casting a polymer composition embodiment of the present inventiononto a surface of a substrate to form a bonding layer thereon (or on apreviously applied polymer layer). Generally such casting isaccomplished using processes such spin coating, spray coating, doctorblading and the like, followed by a baking step for removing essentiallyall of the casting solvent.

The polymer composition embodiments described herein are particularlyeffective at forming relatively thick bonding layers (in someembodiments over 100 μm thick) on a substrate in a single castingapplication, thus making multiple casting applications unnecessary formost desired thicknesses. However, multiple casting applications can beemployed when different polymer layers (polymer layers with differentcharacteristics) are desired and/or advantageous.

In embodiments where a multi-layered film containing at least twodifferent polymer layers is employed one of many alternatives can beselected for forming the bonded structure. For example, a PLA layer canbe formed on a first substrate and a NPL layer is then formed on the PLAlayer, followed by a second substrate attached to the NPL layer. Or aNPL layer can be formed on a first substrate and a PLA layer is thenformed on the NPL layer, followed by a second substrate attached to thePLA layer. Alternatively, a PLA layer can be formed on a first substrateand a NPL layer can be formed on a second substrate, and the twosubstrates are bonded together via the PLA layer and NPL layer. Stillalternatively, a NPL layer can be formed on a first substrate and a PLAlayer can be formed on a second substrate, and the two substrates arebonded together via the NPL layer and PLA layer. For brevity additionalpermutations relating to multi-layered films containing at least threeor more different polymer layers are not described.

It has been found that a bonding layer formed from a polymer compositionembodiment or multi-layered film of the present invention can be used toform a thermal compression bond between surfaces of two substrates. Suchthermal compression bonding employing a first temperature and a firstpressure maintained for an appropriate period of time. It will beunderstood that such first temperature, pressure and time period are afunction of the specific polymer used to form the layer, as well as thelayer's thickness. It will also be understood that the selection of sucha specific polymer or specific polymer layers within a multi-layeredfilm is determined in significant part by the type of substrates to bebonded as well as the nature of any processing that will be performedafter such bonding is completed. For example, where a semiconductorwafer is to be bonded to a carrier substrate to allow for the wafer'sthickness to be reduced, a bonding layer thickness of 5 to 60 microns(or 2 to 50 microns per layer of a multi-layered film) is generallyappropriate and bonding temperatures and pressures can be from 70° C. to260° C. and 0.01 MPa to 10 MPa, respectively. However, where, forexample singulated semiconductor die having electrical connectivitymeans (e.g., solder balls or bumps) are disposed over a surface forbonding such die to a carrier substrate, the thickness of the bondinglayer is selected to be slightly greater than the dimension of suchelectrical conductivity means so that such means remain undamaged duringthe forming of the temporary bond.

In multi-layered film embodiments, the thermal decomposition temperatureof one layer is lower than the thermal decomposition temperature of asecond layer. The thermal decomposition temperature can be lowered by anexternal stimulus such as exposure to actinic radiation or an activechemical species.

Once formed, the bonding layer has a first set of properties related tothe specific polymer selected for the polymer composition or at leastpolymer layer of a multi-layered film that is cast to form such alayer(s). These properties include one or more of T_(mwl) (temperatureof molecular weight lowering) weight average molecular weight (M_(w)),viscosity, T_(g) (glass transition temperature), solubility, adhesion,or any other property that enables the layer(s) to bond one substrate toone another and then, after exposure to a desired amount of actinicradiation at an appropriate wavelength, allow for debonding of suchsubstrates. Such an appropriate wavelength of such actinic radiation istypically from 150 nm to 700 nm, where generally a wavelength of 157 nm,193 nm, 248 nm, 365 nm, 405 nm, 436 nm, and 633 nm is selected. Withregard to the amount of actinic radiation, generally from 1 to 2 Joulesper square centimeter (J/cm²) are appropriate although higher or loweramounts may also be useful.

For polymer composition embodiments of the present invention thatincorporate a PAG therein, the bonding layers formed thereof aresensitive to actinic radiation. It has been found that for suchembodiments, exposing such a bonding layer to an appropriate wavelengthof radiation results in a substantial lowering of the polymer's originalmolecular weight (M_(w)). Advantageously, this lowering of molecularweight results in a lowering of the polymer's viscosity thus allowingfor debonding of any substrates previously attached to one anotherthrough such a bonding layer. For some embodiments, the lowering of themolecular weight has been found to be as much as an order of magnitude.For other embodiments, the lowering of molecular weight has been foundto be about one half of the original molecular weight.

As it will be shown hereinafter, exposure of the bonding layer toactinic radiation does not cause the polymer therein to decompose andrelease gaseous by-products. Rather, it is believed that where a PAG isadded to a polymer the acid formed from the exposure of the included PAGto the aforementioned actinic radiation causes some bond cleavage in thepolymer backbone to occur thus resulting in the observed lowering of thepolymer's M_(w) and the decreased viscosity that allows for debonding.Such a process is referred to herein as depolymerization.

Polymeric decomposition, as observed for other temporary bondingmaterials is, however, necessarily accompanied by the release of gaseousby-products. Such gaseous by-products can result in contamination of oneor both of the bonded substrates thus causing a loss of yield or reducedreliability for a product made using such materials. However, themolecular weight lowering of the instant polymer embodiments is believedto be advantageous over such prior art temporary bonding layers as theaforementioned contamination is essentially eliminated by the absence ofsuch gaseous by-products. Further, any portions of the layer having thelowered molecular weight that remain attached to one or both substratesafter debonding, by either a slide-off or a wedge debonding method, havebeen found to be readily removed by washing with an appropriate solventor solution.

Referring to FIG. 1, a flow chart depicting a method of processing asemiconductor structure in accordance with one aspect of the inventionis shown. FIG. 1 more specifically depicts the method where amultilayered bonding film is employed to temporarily join twostructures. Beginning at Act 10, two substrates are provided, such as asemiconductor substrate or wafer and a support substrate. Act 20involves forming a first polymer layer on one of the two substrates;that is, on one of the semiconductor substrate or the support substrate.Act 30 involves the optional forming of a second polymer layer on one ofthe two substrates. The second polymer layer can be formed over thefirst polymer layer that is already formed or the second polymer layercan be directly formed on the semiconductor substrate or the supportsubstrate that does not have the first polymer layer already formedthereon. Act 40 involves forming a fixable bond between the twosubstrates; that is, between the semiconductor substrate and the supportsubstrate. Regardless of how Act 30 is performed (regardless of wherethe second polymer layer is initially formed), the two substrates arebonded such that the first polymer layer and, if present, the secondpolymer layer are adjacent each other and are positioned between the twosubstrates. Act 50 involves performing one or more processes on one ofthe substrates, typically the semiconductor substrate. The processes aretypically those performed during semiconductor processing and caninclude one or more of etching, thinning, depositing materials,patterning materials, forming structures such as through silicon vias(TSVs), attaching structures, removing structures, testing structures,and the like. Act 60 involves applying an appropriate stimulus, such asactinic energy and/or thermal energy, to the polymer layer(s) to causedepolymerization of at least one of such layers. Act 70 involvesseparating the two semiconductor substrates from each other; that is,separating the semiconductor wafer from the support substrate.

Separation is done in a non-destructive manner such that one or both ofthe two substrates are not irreparably damaged as a result of theseparation act. Advantageously, where two polymer layers are formed, ithas been found that causing depolymerization of the polymer layeradjacent the support substrate is effective in preventing damage to thesemiconductor substrate. Act 80 involves removing any polymer residuesfrom the two substrates. In the case of separating a semiconductorsubstrate from a support substrate, although polymer residues can beremoved from both semiconductor substrate and support substrate, forsome embodiments polymer residues can be removed from only thesemiconductor substrate.

In the presentation of the following experimental data, abbreviationsare used to simplify the naming of polymers, casting solvents and PAGs.The abbreviations used below coordinate with the names and abbreviationspreviously provided for each of the polymers, casting solvents and PAGs.It will also be understood that while specific details for thespin-coating of the exemplary polymer composition embodiments below areprovided, such details are non-limiting and that other spin speeds,times, ramp rates and dispense amounts can be employed to achieve adesired film thickness. Furthermore, it will be noted that theexperimental data provided does not limit the scope of the embodimentsof the present invention. Rather, such data merely illustrate thepreparation of composition embodiments in accordance with the presentinvention as well as for demonstrating the molecular weight loweringdiscussed above and thus the usefulness of such embodiments.

The following examples illustrate the subject invention. Unlessotherwise indicated in the following examples and elsewhere in thespecification and claims, all parts and percentages are by weight, alltemperatures are in degrees Centigrade, and pressure is at or nearatmospheric pressure.

EXAMPLES Example 1A PDL20 Formulation

Polylactide (PDL20) (40 g, 18.1 wt %) was dissolved in (GBL) (180 g).

GSID26-1 (tris(4-(4-acetylphenylthio)phenyl)sulfonium tris(trifluoromethanesulfonyl)methide BASF) (0.8 g, 0.4 wt %) was added tothe polylactide solution. The viscosity was determined with an E-typeviscometer and found to be 20.0 Pa·s at 25° C.

Example 1B Evaluation of Temporary Wafer Bonding Process

The formulation of Example 1A was spin-coated onto an 8 inch glass waferafter which the coated wafer was soft-baked at 120° C. for 5 minutes andthen hard-baked at 220° C. for 5 minutes to give a 40 um thick film. Adevice wafer was then bonded to the coated glass wafer using a SB-8esubstrate bonder (Suss MicroTec) set at a temperature of 170° C. with apressure of 0.2 MPa applied for 5 minutes in a vacuum (10⁻² mbar). Thebonded sample was visually inspected and no voids were observed. Afterthe inspection, the device wafer was mounted on a DFG8540 automaticsurface grinder (Disco) and thinned to a thickness of 50 um. The bondedstack was the exposed through the glass wafer side using a MA-8 exposuretool (Suss MicroTec) to a dose of 2000 mJ/cm² at a wavelength of 365 nm.Then the thinned device wafer was then debonded from the glass wafer bya slide-off method using an EVG 805 wafer debonder (EV Group, Austria)set at a slide-off rate of 2.0 mm/sec and a temperature of 170° C. Theresidue on the device and glass wafers was removed by soaking in GBL at25° C. with agitation.

Example 2A Evaluation of Temporary Wafer Bonding Process

The formulation in Example 1A was spin-coated onto an 8 inch glasswafer, the glass wafer bonded to a device wafer, the device waferthinned and debonded from the glass wafer using the method of Example1B, except that no hard bake was performed. Any residue on device andglass wafer was removed by soaking in GBL at 25° C. with agitation.

Example 3 Evaluations of poly(lactide) Solutions and Films FormedThereof

A number of polymer solutions were prepared by dissolving a specificpolymer in a specific solvent (see Table 2, below). For each solutionhaving a DL content of 100%, dissolution was achieved by rolling thesolvent and polymer mixture overnight at room temperature on a bottleroller. For each solution where the DL content was less than 100%,dissolution was achieved by mixing the solvent and polymer mixtureovernight with a mechanical stirrer while heating the bottle with anelectric heating mantle set at 50° C. The appearance of the solution wasexamined visually to determine if the mixture was clear, hazy, orcontained gel.

Approximately 5 g of each of the polymer solutions was hand dispensedfrom the bottle onto the center of a 4-inch silicon wafer mounted on aCEE-spinner from Brewer Science. After the dispensing of each polymercomposition was completed, the wafer ramped at a rate of 1000 rpm/sec to1400 rpm. After 30 sec, wafer rotation was stopped and the wafer putonto a hot plate at 120° C. for 20 min to remove any residual solvent toprovide a solid film. The film was examined visually to determine if thefilm was smooth or rough.

The film was then scratched manually with a blade to the wafer surfacenear the wafer center. Using a KLA-TENCOR Alpha-step 500 profiler, asingle thickness measurement was performed. See Table 2 for results.

TABLE 2 Appearance of DL Appearance spin coated and Thickness Grade IVcontent Mw Solvent TS (%) Filtration of solution soft baked film (μm)PLDL7025 2.5 dl/g 30 274K GBL 10 No Clear Smooth 6 PLDL7025 2.5 dl/g 30274K NMP 10 No Clear Smooth 6 PDL20 2.0 dl/g 100 330K NMP 20 No ClearSmooth 40 PDL20 2.0 dl/g 100 330K GBL 20 No Clear Smooth 40 PLDL7017 1.7dl/g 30 185K NMP, 20 No Clear Smooth 40 PLDL7017 1.7 dl/g 30 185KCyclohexanone 20 No Clear Smooth 40 PLDL7017 1.7 dl/g 30 185KCyclopentanone 20 No Clear Smooth 40 PLDL7017 1.7 dl/g 30 185K GBL 20 NoHazy Smooth 40 PLDL7006 0.6 dl/g 30  35K GBL 30 No Gel Rough 40 PLDL70060.6 dl/g 30  35K GBL 30 Yes Clear Smooth 13 PLDL7006 0.6 dl/g 30  35KNMP 30 No Hazy Smooth 30 PLDL7008 0.8 dl/g 30  43K GBL 30 No Gel Rough35 PLDL7008 0.8 dl/g 30  43K NMP 30 No Hazy Rough 25 PLDL7010 1.0 dl/g30  57K GBL 30 No Gel Rough 10 PLDL7010 1.0 dl/g 30  57K NMP 30 No ClearSmooth 30 PLDL8416 1.68 dl/g  16 116K GBL 30 No Not soluble — — PLDL84161.68 dl/g  16 116K NMP 30 No Not soluble — — PDL02 0.2 dl/g 100 13.7KGBL 50 No Clear Smooth 23 PDL02 0.2 dl/g 100 13.7K NMP 50 No ClearSmooth 20 PDL05 0.5 dl/g 100 37.6K GBL 30 No Clear Smooth 32 PDL05 0.5dl/g 100 37.6K NMP 30 No Clear Smooth 27 PDL05 0.5 dl/g 100 37.6K NMP 50No Clear Smooth 115 PDL05 0.5 dl/g 100 37.6K GBL 45 No Clear Smooth 48PDL05 0.5 dl/g 100 37.6K NMP 45 No Clear Smooth 38

Example 4 Effect of UV Exposure on Mw

A formulation of PLDL7017 and GSID26-1 in NMP (20% TS (Total Solids),0.5 phr GSID26-1) was prepared and spin coated onto each of three 4-inchSi wafers. After coating, each wafer was soft baked at 120° C. for 20min and the thickness of the film determined to be 40 μm. The M_(W) ofpolymer in the formulation was determined using GPC (Gel PermeationChromatography). The film on the first wafer was hard baked at 210° C.for 5 min. The film on the second wafer was hard baked at 200° C. for 5min. A portion of the film from these two wafers was then scraped fromthe wafers and the M_(W) of each scraped portion was determined usingGPC.

A formulation of PDL20 and GSID26-1 in GBL (20% TS, 0.5 phr GSID26-1)was prepared and spin coated onto each of three 4-inch Si wafers. Aftercoating, each wafer was soft baked at 120° C. for 20 min and thethickness of the film determined to be 40 μm. The M_(W) of PDL20 in theformulation was determined using GPC. The film on the first wafer washard baked at 170° C. for 5 min. The film on the second wafer was hardbaked at 180° C. for 5 min. A portion of the film from these two waferswas then scraped from the wafers and the M_(W) of each scraped film wasdetermined using GPC.

With UV Exposure:

The third wafer having the PLDL7017/GSID26-1 formulation spun thereon toform a film was then exposed, using an AB-M mask aligner, to a dose of 2J/cm² at a wavelength of 365 nm followed by hard bake at 200° C. for 5min. A portion of the film was then scraped from the wafer and the M_(W)of the scraped portion determined using GPC.

The third wafer having the PDL20/GSID26-1 formulation spun thereon toform a film was then exposed, using an AB-M mask aligner, to a dose of0.1 J/cm² at a wavelength of 365 nm followed by hard bake at 170° C. for5 min. A portion of the film was then scraped from the wafer and theM_(W) of the scraped portion determined using GPC.

The results of each of the six wafers are provided in Table 3, below:

TABLE 3 Wafer UV Hard Original M_(w) after No. Formulation Exposure BakeM_(w) hard bake PLDL7017/ None 210° C. 185K 177K GSID26-1 PLDL7017/ None200° C. 198K 211K GSID26-1 PLDL7017/   2 J/cm² 200° C. 185K  27KGSID26-1 PDL20/GSID26-1 None 170° C. 342K 320K PDL20/GSID26-1 None 180°C. 324K 311K PDL20/GSID26-1 0.1 J/cm² 180° C. 342K  46K

Example 5

A formulation of PDL20 and GSID26-1 in GBL (20% TS, 2 phr GSID26-1) wasprepared and spin coated onto a 4-inch Si wafer. After coating the waferwas baked at 120° C. for 20 min to remove residual GBL, blanket exposedto 2000 mJ/cm² of actinic radiation having a wavelength of 365 nm andbaked after exposure at 200° C. for 15 min in a N₂ purged oven. Theweight of the substrate and film was determined after the first bake,after the 2000 mJ/cm² exposure and after the second bake to be 8.66 g,8.66 g and 8.66 g, respectively. Two additional samples of the abovepolymer composition were cast onto 4-inch Si wafers by spin coating. Aportion of the film was then scraped from one of the samples and theM_(W) of the scraped portion determined to be 316,800 using GPC. Thesecond sample was exposed, using an AB-M mask aligner, to a dose of 2000m J/cm² at a wavelength of 365 nm followed by hard bake at 200° C. for15 min. A portion of the film was then scraped from the wafer and theM_(W) of the scraped portion determined to be 25,500 using GPC.

Example 6A Random MMA-MAA Copolymer

Methyl methacrylate-methacrylic acid (80/20) copolymer (5 g,Monomer-Polymer and Dajac Labs, product number 9425) was dissolved insufficient cyclopentanone to give a 40 weight percent solution.Approximately 2 g of this solution was hand dispensed onto the center ofa 4-inch silicon wafer. The wafer was spun at 1000 rpm for 30s. Thewafer was baked at 120° C. for 20 min. The resulting crack free film wasdetermined to be 48 um thick.

A second portion of methyl methacrylate-methacrylic acid (80/20)copolymer was dissolved in cyclopentanone (17 g) to give a 15 weightpercent solution. Approximately 2 g each of this solution was handdispensed onto the center of two 4-inch silicon wafer. The wafers werespun at 500 rpm for 70 sec. The wafers were baked at 130° C. for 2 min.One wafer was exposed (1J/cm² at 248 nm) in an Electro-lite CorporationElectro-Cure 4001 UV Flood System equipped with an Electro-lite bulb(part #82058). This wafer was then post exposure baked at 150° C. for 15min. A sample of polymer was scraped from each of the exposed and theunexposed wafers. GPC analysis of these two polymer samples showed thatthe Mw of the exposed portion of the polymer was substantially decreasedcompared to the unexposed portion of polymer. In a separate experiment,another wafer was prepared and exposed as stated above and thensubmitted for GPC analysis.

TABLE 4 Sample Mw Mn Mw/Mn Polymer as received 33110 17181 1.93Unexposed polymer 31500 16800 1.88 Exposed polymer 10200 3390 3.08Exposed polymer (repeat) 5670 3060 1.85

A four inch silicon wafer was weighed with a 4 decimal place analyticalbalance. A portion of the 15 wt % solution described above was spincoated onto a silicon wafer at 500 rpm for 30 sec. The weight of thewafer was determined after a 120° C. 20 min post apply bake. The entirewafer was exposed (2 J at 248 nm) in an Electro-lite CorporationElectro-Cure 4001 UV Flood System. The weight of the wafer wasdetermined after exposure. The wafer was then post exposure baked at150° C. for 15 min. Once again, the weight of the wafer was determined.

TABLE 5 Sample g Wafer weight prior to polymer solution spinning 14.4929Wafer + polymer film weight after post apply bake 15.2118 Wafer +polymer film weight after exposure 15.2045 Wafer + polymer film weightafter post exposure bake 15.1534

As calculated from the tabulated results, above, the weight of polymeron the wafer after post apply bake was 0.7189 g; after exposure, 0.7116g; and after post exposure bake 0.6605 g. Throughout the process, thetotal amount of material lost was minimal, 0.0584 g or approximately 8%.

Example 6B

Three 15 weight percent polymer solutions of methylmethacrylate-methacrylic acid (80/20) copolymer were prepared as aboveand then one percent, by weight of the polymer, of one of CPTX(1-chloro-4-propoxy-9H-thioxanthone, Lambson Group Inc.),2,2-dimethoxy-2-phenyl acetophenone (Sigma Aldrich) and benzophenone wasadded to each solution. Approximately 2 g each of these solutions werehand dispensed onto the center of three separate 4-inch silicon wafer.The wafers were spun at 500 rpm for 70 sec. The wafers were post applybaked at 130° C. for 2 min. The wafers were exposed using an ABM maskaligner (dose 1 J/cm2 at 365 nm). Then the wafers were post exposurebaked at 150° C. for 15 min. A sample of polymer was scraped from eachof the wafers and submitted for GPC. The experiment was then repeatedtwice, once with an exposure dose of 10 J/cm2, and once withoutexposure, for the unexposed samples, the wafers were not post exposurebaked. A sample of polymer was scraped from each of the wafers andsubmitted for GPC. The results of these experiments are shown in thetable below.

TABLE 6 Dose Sample photosensitizer (J/cm2) PEB? Mw Mn Mw/Mn Polymer as— — No 33110 17181 1.93 received Exposed polymer CPTX 1 Yes 31200 171001.82 Exposed polymer CPTX 10 Yes 30400 16500 1.84 Exposed polymer CPTX 1No 31400 17400 1.81 Exposed polymer CPTX 10 No 30500 16600 1.83 Exposedpolymer 2,2-dimethoxy-2-phenyl 1 Yes 31400 17500 1.80 acetophenoneExposed polymer 2,2-dimethoxy-2-phenyl 10 Yes 31000 17000 1.82acetophenone Exposed polymer 2,2-dimethoxy-2-phenyl 1 No 31400 173001.81 acetophenone Exposed polymer 2,2-dimethoxy-2-phenyl 10 No 3130017100 1.83 acetophenone Exposed polymer benzophenone 1 Yes 31500 171001.84 Exposed polymer benzophenone 10 Yes 31800 17100 1.86 Exposedpolymer benzophenone 1 No 32000 17400 1.84 Exposed polymer benzophenone10 No 31900 17400 1.83

As shown in Table 4, exposure at 248 nm results in significant molecularweight decrease. Table 5 shows that exposure to 248 nm light does notresult in an inordinate loss of polymer weight even after post exposurebake, and Table 6 shows that, even with photosensitizers, exposure at365 nm does not result in a reduction in Mw. Therefore the expecteddecrease in melt viscosity and debonding temperature would not beexpected to occur upon exposure at 365 nm.

Example 6C

Approximately 2 g each of the aforementioned 15 wt % solution was handdispensed onto the center of two 4-inch silicon wafer. The wafers werespun at 500 rpm for 70 sec. The wafers were baked at 130° C. for 2 min.One wafer was exposed (1 J/cm2 at 248 nm) using an ABM mask alignerwithout a 365 nm band pass filter. The other wafer was exposed (10 J/cm2at 248 nm) using an ABM mask aligner without a 365 nm band pass filter.A sample of polymer was scraped from both wafers. GPC analysis of thesetwo polymer samples showed that the Mw of both polymers did not changesignificantly from the as received polymer.

TABLE 7 Sample Mw Mn Mw/Mn Polymer as received 33110 17181 1.93 1 J/cm2exposed polymer 31700 17800 1.78 10 J/cm2 exposed polymer 31600 180001.75

Example 7

Methyl methacrylate-butyl acrylate triblock copolymers (LA 2250, LA 4285and LA 2140e from Kuraray) were dissolved in cyclopentanone solution tomake a 40 wt % solution. Approximately 2 g of each solution was handdispensed onto the center of a 4-inch silicon wafer. The wafer was spunat 500 rpm for 70 sec. The wafer was baked at 120° C. for 5 min. Thefilm thickness of the resulting crack free films was determined byprofilometry.

TABLE 8 Polymer LA 2250 LA 4285 LA 2140e Film Thickness (um) 30.1 44.629.4

Approximately 2 g of the 40 wt % methyl methacrylate-butyl acrylatetriblock copolymers (LA 4285 from Kuraray) solution in cyclopentanone asdescribed above was hand dispensed onto the center of each of two 4-inchsilicon wafers. The wafers were spun at 500 rpm for 70 sec. The waferswere baked at 120° C. for 5 min. One wafer was exposed (2J/cm² at 248nm) in an Electro-lite Corporation Electro-Cure 4001 UV Flood Systemequipped with an Electro-lite bulb (part #82058). This wafer was thenpost exposure baked at 150° C. for 15 min. A sample of polymer wasscraped from the exposed and the unexposed wafers. GPC analysis of thesetwo polymer samples showed that the M_(W) of the exposed portion of thepolymer was substantially decreased compared to the unexposed portion ofpolymer.

TABLE 9 Exposure using Electro-Cure 4001 UV Flood System Sample Mw MnMw/Mn Polymer as received 59900 51900 1.15 Unexposed polymer 60000 530001.13 Exposed polymer 40150 4180 9.61

The above experiment was repeated except the exposure was carried outusing an ABM mask aligner (2J/cm² at 248 nm) without a 365 nm band passfilter. GPC results of the exposed and unexposed polymers are shown inTable 10, below.

TABLE 10 Exposure using ABM mask aligner Sample Mw Mn Mw/Mn Polymer asreceived 59900 51900 1.15 Unexposed polymer 59600 52300 1.14 Exposedpolymer 59600 52500 1.13

The Table 9 and 10 data shows that the exposed polymer using theElectro-Cure Flood System results in a drop in molecular weight whilethe molecular weight of the polymer exposed using the ABM mask aligneris unaffected.

As the above results are unexpected, a subsequent experiment wasperformed to compare wafer temperatures between exposure using theElectro-lite Corporation Electro-Cure 4001 UV Flood System equipped withan Electro-lite bulb (part #82058) and using the ABM mask alignerwithout a 365 nm band pass filter. The exposures were performed usingblank silicon wafers and a Fisher Scientific Traceable NoncontactInfrared Thermometer to measure the temperature of the silicon wafersbefore and after exposure. As seen in Table 11, the temperature of thewafer exposed using the UV Flood system was 63° C. higher than that ofthe wafer exposed using the mask aligner. Therefore it is believed thata combination of exposure and heat resulted in the substantial reductionin Mw.

TABLE 11 Temperature before Temperature after Exposure unit exposureexposure Electro-Cure 4001 UV 22° C. 91° C. Flood System ABM Maskaligner 19° C. 28° C.

Example 8

An appropriate amount of RV270, an amorphous copolyester, (ToyoboAmerica, Inc.) was dissolved in cyclopentanone along with 0.5 wt %polymer of GSID26-1 (tris(4-(4-acetylphenylthio)phenyl)sulfonium tris(trifluoromethanesulfonyl)methanide, BASF) to give a 46 weight percentsolution. Approximately 2 g of this solution was hand dispensed onto thecenter of a 4-inch silicon wafer. The wafer was spun at 1800 rpm for 30sec. The wafer was baked at 120° C. for 5 min resulting in 50 um thick,crack-free film.

Portions of the above RV270 solution were spin coated onto each of twosilicon wafers in the manner described above. One wafer was exposed (2J/cm² at 365 nm) with an AB-M mask aligner system while the other waferwas not. The exposed wafer was then post exposure baked at 200° C. for 5min on a CEE 1300X hot plate. Polymer samples were scraped off theexposed wafer and the unexposed wafers. The GPC analysis of these twopolymer samples, shown in Table 12, demonstrated that the M_(w) of theexposed polymer was substantially lowered from that of the unexposedpolymer.

TABLE 12 Sample Mw Mn Mw/Mn Unexposed polymer 50009 23967 2.08 Exposedpolymer 17501 8853 1.97

Example 9

An appropriate amount of GK880, an amorphous copolyester, (ToyoboAmerica, Inc.) was dissolved in cyclopentanone along with 1.5 wt %polymer of GSID26-1 to give a 48 weight percent solution. Approximately2 g of this solution was hand dispensed onto the center of a 4-inchsilicon wafer. The wafer was spun at 1800 rpm for 30 sec and then bakedat 120° C. for 5 min resulting in 30 um thick, crack-free film.

Portions of the above GK880 solution were spin coated onto each of twosilicon wafers in the manner described above. One wafer was exposed (2J/cm² at 365 nm) with an AB-M mask aligner system while the other waferwas not. The exposed wafer was then post exposure baked at 200° C. for 5min on a CEE 1300X hot plate. Polymer samples were scraped off theexposed wafer and the unexposed wafers. The GPC analysis of these twopolymer samples, shown in Table 13, demonstrated that the M_(W) of theexposed polymer was substantially lowered from that of the unexposedpolymer.

TABLE 13 Sample Mw Mn Mw/Mn Unexposed polymer 55883 18875 2.96 Exposedpolymer 10423 4788 2.17

A four inch silicon wafer was weighed with a 4 decimal place analyticalbalance. A portion of the RV270 solution was applied to a silicon waferin the manner described above. The weight of the wafer was measuredafter the 120° C., 5 min post apply bake. The entire wafer was exposed(2 J/cm² at 365 nm) with an ABM mask aligner with a band pass filter.The weight of the wafer was determined after exposure. The wafer wasthen post exposure baked at 200° C. for 5 min on a CEE 1300X hot plate.Once again, the weight of the wafer was determined. As shown in Table14, the weight of the wafer+polymer is essentially unchanged.

TABLE 14 Sample g Wafer + polymer film weight after post apply bake9.1678 Wafer + polymer film weight after exposure 9.1666 Wafer + polymerfilm weight after post exposure bake 9.1640

Example 10

A terpolymers of 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid and 2,2-dimethyl-1,3-propanediol wasprepared under catalyzed condensation reaction conditions as describedbelow. In a dry box, the three monomers (all purchased from SigmaAldrich) were weighed and added to a 250 ml of round bottom flaskequipped with a stir bar. The monomer mixture contained 25.0 g (0.145mol) of 1,4-cyclohexanedicarboxylic acid, 13.0 g (0.076 mol) of1,3-cyclohexanedicarboxylic acid, and 25.3 g (0.243 mol) of2,2-dimethyl-1,3-propanediol. Then, 0.073 g of triethylamine and 0.26 gof titanium (IV) 2-ethyl-hexyloxide were added respectively. Thereaction set-up was assembled in the hood with the reaction flaskconnected to a vacuum line in a way that the vacuum could be controlledunder a N₂ atmosphere. The reaction mixture was heated to 200° C. for100 min. at 1 atm with water from the reaction being collected in a coldtrap. Then the pressure was reduced to 4 Torr and the reaction was heldfor an additional 2 hr. The temperature was further increased to 230° C.and the pressure was further decreased to 0.5 Torr and allowed to reactfor an additional 6 hr before it was stopped. GPC analysis showed theproduct having an Mw of 62,226, Mn of 31,234, and PDI of 1.99.

To test the film forming quality of the above terpolymer, an appropriateamount was dissolved in cyclohexanone to give a 45 wt % solution. Thesolution was then filtered through a 0.45 μm PTFE filter and a portionhand dispensed onto a silicon wafer and spin coated thereon at 700 rpmfor 30 sec. After a 5 min bake at 120° C. a crack free, 40 μm film wasobtained.

Portions of the terpolymer solution were then further formulated withone of TPS-C1 (5 phr) for 248 nm exposure and GSID26-1 (2 phr) for 365nm exposure, respectively. A silicon wafer was then coated with eachsolution, as described above, and then exposed at 248 nm (2 J/cm²) and365 nm (2 J/cm²) accordingly. For the formulation using TPS-C1, theElectro-lite Corporation Electro-Cure 4001 UV Flood System equipped withan Electro-lite bulb (part #82058) was used for exposure. For theformulation using GSID26-1 the AB-M mask aligner system equipped with aband pass filter was used for exposure. The molecular weights of eachpolymer was determined by GPC analysis before and after exposure andreported in Tables 15 and 16, respectively.

TABLE 15 Exposure at 365 nm Sample (5 phr TPSC-1) Mw Mn Mw/Mn Unexposedpolymer 56247 27182 2.07 Exposed polymer 15781 6483 2.43

TABLE 16 Exposure at 248 nm Sample (2 phr GSID26-1) Mw Mn Mw/MnUnexposed polymer 57057 32012 1.78 Exposed polymer 44980 24479 1.84

As the lowering of the Mw for the terpolymer formulation having a 2 phrGSID26-1 loading was less than anticipated, a formulation having 8.3 phrGSID26-1 was prepared as this loading is the molar equivalent of the 5phr TPSC-1 loading in the other formulation. A wafer coated with thisnew solution was prepared and exposed as before and the molecular weightof exposed and unexposed samples determined. As shown in Table 17, theM_(W) demonstrated by the exposed polymer was essentially equivalent tothe lowering seen for the 5 phr TPS-C1 solution reported in Table 15(31% v. 28%).

TABLE 17 Sample (8.3 phr GSID26-1) Mw Mn Mw/Mn Unexposed polymer 5878526045 2.26 Exposed polymer 18013 4581 3.93

Example 11

Ethyl cellulose (15 g, Aldrich, 48% ethoxyl content) was dissolved in an80:20 mixture of toluene (68 g) and ethanol (17 g) to give a 15 weightpercent solution. Approximately 2 g of this solution was hand dispensedonto the center of a 4-inch silicon wafer. The wafer was spun at 500 rpmfor 70 sec. The wafer was baked at 120° C. for 5 min resulting in acrack-free 22 um thick film.

Another ethyl cellulose formulation was prepared with NMP/butanol as thesolvent and a TPS-C1 photoacid generator (PAG) as follows: ethylcellulose (1.00 g, Aldrich, 48% ethoxyl content) was dissolved in NMP(3.2 g) and butanol (0.8 g) along with TPS-C1 (0.05 g) to give anapproximate 20 wt % solution of ethyl cellulose with approximately 5 wt% PAG on the polymer.

This second formulation was then spin coated onto a silicon wafer asdescribed above and half the wafer exposed (2 J/cm² at 248 nm) in anElectro-lite Corporation Electro-Cure 4001 UV Flood System while theother half was not exposed. The whole wafer was then post exposure bakedat 150° C. for 15 min. A sample of polymer was scraped off of theexposed and the unexposed portions of the wafer and the Mw of eachdetermined by GPC analysis. The molecular weight of each sample areshown in Table 18, below.

TABLE 18 Sample Mw Mn Mw/Mn Polymer as received 143000 48600 2.93Unexposed polymer 101000 42100 2.39 Exposed polymer 57400 3390 16.9

As it can be seen the exposed polymer exhibited substantial M_(W)lowering.

A four inch silicon wafer was weighed with a 4 decimal place analyticalbalance. A portion of the second ethyl cellulose solution was spincoated onto a silicon wafer as described above. The weight of the waferwas measured after the 120° C. 5 min post apply bake. The entire waferwas then exposed (2 J at 248 nm) in an Electro-lite CorporationElectro-Cure 4001 UV Flood System equipped with an Electro-lite bulb(part #82058) and the weight of the wafer measured. The wafer was thenpost exposure baked at 150° C. for 15 min and once again the weight ofthe wafer measured. The several weights are provided in Table 19, below.

TABLE 19 Sample g Wafer weight prior to polymer solution spinning 9.8543Wafer + polymer film weight after post apply bake 10.3029 Wafer +polymer film weight after exposure 10.2929 Wafer + polymer film weightafter post exposure bake 10.2799

As the data in Table 19 indicates, the total weight loss of polymer isminimal.

A portion of the second ethyl cellulose formulation was spin coated ontoa silicon wafer as described above. One half of the wafer was exposed (2J/cm² at 248 nm) with an ABM mask aligner without a 365 nm band passfilter while the other half was not exposed. The whole wafer was thenpost exposure baked at 150° C. for 15 min. A sample of polymer wasscraped off of the exposed and the unexposed portions of the wafer andthe Mw of each determined by GPC analysis. The molecular weight of eachsample are shown in Table 20, below.

TABLE 20 Sample Mw Mn Mw/Mn Unexposed polymer 115,000 23600 4.88 Exposedpolymer 114,000 32500 3.51

As the data in Table 20 indicates, M_(w) is essentially unchangedbetween the exposed and unexposed polymer samples.

Example 12 Bi-Layer Example

First polymer layer: Commercial poly(lactide) (PLD20; PURAC biochemBV)(40 g, 22.1 wt %) was dissolved in gamma-butyrolactone (GBL) (140 g).Tris(4-(4-acetylphenylthio)phenyl)sulfoniumtris(trifluoromethanesulfonyl)methide (GSID26-1; BASF) (0.8 g, 0.4 wt %)was added to the poly(lactide) solution and the viscosity, 20 Pas at 25°C., determined with an E-type viscometer.

Second polymer layer: A norbornene-type polymer derived from hexylnorbornene and AOAO norbornene was prepared by well-known vinyl additionpolymerization (see, U.S. Pat. No. 8,053,515 and U.S. Pat. No.7,932,161, the pertinent parts of which are incorporated herein byreference), was dissolved in mesitylene to form a non-photosensitivepolymer solution.

The formulation of the first polymer layer was spin-coated onto a 8 inchglass wafer. The coated wafer was soft-baked at 180° C. for 20 minutesin oven to give a 5 μm film. The formulation of the second polymer layerwas spin-coated over the first polymer layer providing a double-coatedglass wafer. The double coated glass wafer was then soft-baked at 120°C. for 20 minutes in oven to give a 70 μm thick bi-layer film thereon.

A device wafer was then bonded to the coated wafer (to the secondpolymer layer) using the substrate bonder SB-8e (Suss MicroTec) at 250°C. with pressure of 0.6 MPa applied for 5 minutes in a vacuum (below10⁻² mbar). The bonded wafer stack was visually inspected through theglass wafer and no voids were observed.

After the inspection, the wafer stack was set onto a wafer grinderDFG8540 (Disco) with the device wafer positioned for wafer thinning andthen thinned to a final thickness of 50 um. After removal from thegrinder, the wafer stack was exposed through the glass wafer to actinicradiation using MA-8 (Suss MicroTec) mask aligner; the exposure dose was2000 mJ/cm² at a wavelength of 365 nm. The thinned device wafer was thenreleased from the glass wafer by a slide-off method using an EVG 805debonder (EV group) set at a slide-off rate of 2.0 mm/sec and atemperature of 160° C.

The residue on the device and glass wafer was removed by soaking in GBLat 25° C. with agitation until all residue was removed.

By now it should be understood that the present disclosure demonstratesa variety of types of polymers that can advantageously be employed toform a temporary (releasable) bond between a device wafer and a glasssubstrate. Further it has been shown that such a release can be effectedat a temperature at or below the temperature at which the temporary bondwas formed. Still further is has been shown that a variety of polymertypes can undergo depolymerization that provides for the release of thedevice wafer from the glass substrate where such depolymerization ischaracterized by a significant lowering of a polymer's M_(w) and theattendant lowering of the polymer's viscosity, thus allowing for eitherslide-off or wedge-off debonding to be accomplished. Exemplary polymertypes that can undergo depolymerization include, but are not limited to,PLA polymers, polycarbonates, polyesters, polyamides, polyethers,polymethacrylates, polynorbornenes, alkylcelluloses and combinations oftwo or more thereof.

While the disclosure has been explained in relation to certainembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the disclosure ofthe various embodiments hereinabove is intended to cover suchmodifications as such will necessarily fall within the scope of theappended claims. For example, while specific spin coating parameterswere provided in the above examples, one of ordinary skill in the artwill understand that by varying such parameters (e.g. dispense volumeand method, choice of casting solvent, viscosity, exhaust, acceleration,spin speed and time) it is possible to form thicker or thinner bondinglayers than disclosed hereinabove.

What is claimed is:
 1. A method of producing a semiconductor devicecomprising: forming a first polymer layer over a first surface of afirst substrate; forming a second polymer layer over the first polymerlayer or over a first surface of a second substrate, where one of thefirst polymer layer and the second polymer layer comprise adepolymerizable polymer backbone; fixably attaching the first substrateto the second substrate through the first polymer layer and the secondpolymer layer; processing a second surface of one of the first substrateor the second substrate; after the processing, causing one of the firstpolymer layer or the second polymer layer to depolymerize at atemperature at or below 200° C.; separating the first substrate from thesecond substrate; and wherein one of said first polymer layer and saidsecond polymer layer comprises a photoacid generator or aphotosensitizer and at least one of said first polymer layer or one ofsaid second polymer layer contains a polylactide.
 2. The method of claim1, where the first substrate is a semiconductor wafer and the firstpolymer layer and the second polymer layer are formed overlying a firstsurface of the semiconductor wafer.
 3. The method of claim 2, where thefirst surface of the semiconductor wafer comprises metallic structuresthat extend above such first surface, such structures being coated bythe forming of one of the first polymer layer or the second polymerlayer.
 4. The method of claim 2, where fixably attaching comprisescontacting the overlying second polymer layer to the first surface ofsecond substrate.
 5. The method of claim 4, where the second substrateis a glass substrate.
 6. The method of claim 2, where after theprocessing, the second polymer layer is depolymerized.
 7. The method ofclaim 1, where the first polymer layer and the second polymer layer areformed overlying the first surface of the first substrate.
 8. The methodof claim 7, where after the processing, the first polymer layer isdecomposed.
 9. The method of claim 1, where one of said photoacidgenerator or a photosensitizer is(tris(4-(4-acetylphenvithio)phenyl)sulfonium tris(trifluoromethanesulfonvl)methide.
 10. The method of claim 1, wherecausing one of the first polymer layer or second polymer layer todepolymerize comprises exposing the layer to actinic radiation effectivefor generating a photoacid and heating to a temperature effective tocause the first polymer layer or the second polymer layer todepolymerize.
 11. The method of claim 1, where causing one of the firstpolymer layer or second polymer layer to depolymerize comprises exposingthe layers to a temperature effective to cause the first polymer layeror the second polymer layer to depolymerize.
 12. A semiconductor deviceproduced by the method of claim 1.